Wildlife matters

The management of waterbirds on a wildlife ranch

30 November 2015

Game birds can be divided into terrestrial and waterbirds. Many wildlife ranchers and hunters still regard game birds as inferior and only shoot them for the pot. However, when a hunter is properly equipped with a trained hunting dog and follows the correct code of conduct by only shooting birds on the wing, wingshooting packages can be added to complement other hunting packages. South Africa has 17 species of indigenous waterbird that can be hunted, but some are protected and may not be hunted, but the spur-winged goosePlectropterus gambensis, the Egyptian gooseAlopochen aegyptiaca and the yellow-billed duckAnas undulata are popular for hunting. There are also numerous types of waterbird that can be used for tourism.

The waterbird habitat in South Africa has changed considerably with time because suitable water surfaces have been created artificially, and many natural wetlands were drained and pans were ploughed up or destroyed by overgrazing. By applying sensible management techniques, any suitable habitat can be improved for waterbirds. The resultant natural increase among game birds can be harvested annually by hunting without harming the nucleus of the breeding population. Managing land for waterbirds too will benefit wildlife conservation and the health of ecosystems.

The best habitat for waterbirds is rivers, wetlands, pans and dams, and the available open water surfaces have increased because of the construction of large dams. Moreover, many smaller artificial dams on wildlife ranches have contributed to a more permanent and widely spread habitat for waterbirds, while wetlands can be constructed when rehabilitating severe soil erosion.

Before artificial water surfaces were available, waterbirds often had to migrate seasonally to suitable habitat. When waterbirds moult they cannot fly for a few weeks and during this period it is important that there are suitable large water surfaces where they are protected against predators. During the breeding season, dams, wetlands and pans provide an important habitat when the waterbirds are dispersed and often occur in pairs.

The primary habitat requirements for waterbirds are a suitable water surface, food source and cover. A combination of deep water where the birds feel safe from predators and shallow water where they can feed and rest is ideal. Part of a shallow shore should also have dense vegetation for additional shelter and nesting. The rest of the vegetation along a shallow shore can be kept short so that the waterbirds can see far enough to feel safe when feeding.

Dams with dense, tall trees along the banks are unsuitable for waterbirds because the trees restrict their vision and flight. A suitable shelter may be provided by constructing either an island with no vegetation where many birds can rest, or an island with sufficient vegetation where some birds can nest. A bare, anchored or floating island may attract waterbirds when there are not sufficient nesting sites around a dam. Islands with high, vertical banks are, however, less suitable for waterbirds than ones with sloping banks, larger islands are better than small ones, and several islands are better than a single one.

Wetlands and pans often dry up during the dry season and the creation of a permanent source of water is then advisable. Wetlands and pans provide suitable waterbird habitat when they maintain relatively shallow water levels and have ample aquatic vegetation. When pans or wetlands become overgrown with reeds, patches of reed can be removed during the dry season so that open water surfaces are again available during the wet season. In rivers, extensive habitat improvement is usually impractical because of floods, although anchored floating islands can make a river more suitable for waterbirds.

Waterbirds mainly feed on aquatic plants and insects, but they will also eat grain when it is available. Aquatic plants and insects will occur naturally in suitable waterbird habitat, but grain may be fed as a supplement. Waste grain that is used for supplementary feeding should preferably be scattered on a bare or short-grass shoreline and in shallow water. As waterbirds usually feed in the late afternoon, this is the best time to put out the grain. It is also preferable to put out small amounts of grain regularly rather than large amounts at one time. Surplus grain that is not eaten immediately ferments and is then unsuitable as food for waterbirds. The cultivation of patches of grain near dams and wetlands will lure more waterbirds to a dam.

Dams with only a few aquatic plants may be improved by transplanting natural food plants from established dams into shallow water. Not only will these plants provide food for the waterbirds, but the aquatic insect population will increase and be used as food by ducklings and other waterbirds. The population of aquatic insects can also be encouraged by scattering manure or compost in shallow water at a ratio of 500 kg per ha of water surface during the spring when most waterbirds breed. However, large amounts of manure or compost on a regular basis should be avoided because it causes overfertilization and creates a deficiency of oxygen for fishes and aquatic insects. Excessive growth of algae is a symptom of overfertilization.

The profile of the dam is important because large areas of shallow water are necessary for feeding waterbirds, but there should also be adjacent areas of deep water where the birds can take refuge from predators. Where the incline of the land on which a dam is built causes it to become too deep too quickly, a shallow water area should be created near the edges by removing the topsoil before the dam is constructed, and depositing it under the water near the shore after the dam has been completed.

Although waterbirds live mostly on the water, they often breed away from it. Most waterbirds prefer to nest in established vegetation such as dense grass and reeds. It is therefore important to provide this kind of habitat around a dam. However, the shelduck Tadorna cana breeds in aardvark burrows near suitable dams or wetlands. When a dam occurs in an area where cattle also graze regularly, a part of the shore may be fenced off to protect the shores from being trampled. Areas with dense shore vegetation, or even islands with dense vegetation, will provide suitable breeding shelter for most waterbirds.

On suitable islands, artificial nests may be set out for waterbirds to provide places to breed. Wooden boxes with rounded corners and lined with cut grass are suitable for nesting. The ideal nesting box measures approximately 300 x 300 mm and is 150 mm high. An entrance of 150 mm wide should be made in one side so that the bottom edge of the entrance is about 20 to 30 mm above the ground. A hive basket that is 800 mm long with an entrance of 150 mm in diameter can also be used as an artificial nest when it is mounted on a trestle frame in shallow water. The basket should be mounted in such a way that the opening faces upwards at an angle of 30°.

All the waterbirds of South are sensitive to regular disturbances and when areas are set aside especially for them, humans and animals such as cattle and dogs should be kept out of the area as far as possible. An ordinary mesh fence that is 1.2 m high around a dam or wetland will prevent such disturbances. Hides can allow people to view the birds at suitable locations.

Before the reintroduction of any waterbirds is considered, the reasons for their absence in the first place has to be determined. In most cases it is the habitat that has become unsuitable and it is then futile to reintroduce waterbirds until the habitat has been rehabilitated. Once the habitat has been rehabilitated, waterbirds will soon discover the dam or wetland and will appear there on their own after flying in early in the morning or late in the afternoon. However, just as they may appear suddenly they may also disappear again unexpectedly.